
%0 Journal Article
%A Hayman, Colin M. 
%A Hanton, Lyall R. 
%A Larsen, David S. 
%A Guthrie, Jenness M. 
%T A Stereoselective Synthesis of 2,6-Dideoxy-6,6,6-trifluoro-<emph type="2">arabino</emph>-hexoses via an Asymmetric Diels&#8211;Alder Strategy
%J Australian Journal of Chemistry
%D 1999/12/03
%V 52
%N 10
%P 921-928
%K 
%R https://doi.org/10.1071/CH99067
%U https://www.publish.csiro.au/paper/CH99067 
%X The enantioselective syntheses of each enantiomer of ethyl 2,6-dideoxy-6,6,6-trifluoro-&#946;-arabino-hexopyranoside (3) and of 2,6-dideoxy-6,6,6-trifluoro-arabino-hexose (4) are described. The key step in the approach is the inverse electron demand Lewis acid catalysed Diels&#8211;Alder reaction of the heterodiene (E)-1,1,1-trifluoro-4-&#91;(1R)-1- phenylethoxy&#93;but-3-en-2-one (5) and either ethyl vinyl ether (7a) or benzyl vinyl ether (7b). The titanium(IV) chloride catalysed cycloadditions at low temperature displayed high endo-selectivity and modest diastereofacial selectivity. Hydroboration of the mixture of the cis-cycloadducts (8a) afforded the separable diastereoisomers (9a) and (10a). Hydrogenolysis of (9a) gave ethyl 2,6-dideoxy-6,6,6-trifluoro-&#946;-L-arabino-hexopyranoside (+)-(3), and of (10a) gave the corresponding D-glycoside (&#8722;)-(3). Similarly, hydroboration of the cis-cycloadducts (8b) gave the protected benzyl glycosides (9b) and (10b). Hydrogenolysis of each gave 2,6-dideoxy-6,6,6-trifluoro-L-arabino-hexopyranose (&#8722;)-(4) and the corresponding D-sugar (+)-(4) respectively. The absolute configurations of fluorinated carbohydrates (+)- and (&#8722;)-(3) were determined by comparison of their molar rotations with those of the parent glycosides. These assignments were confirmed by an X-ray crystallographic structure determination of the glycoside (9a). 
